EP3704790A1 - Method for determining the rotor position of synchronously running electric machines without a mechanical sensor - Google Patents

Abstract

The invention relates to a method for the sensor-free determination of the rotor position of a synchronously running three-phase machine (4), which is supplied via an inverter (3), wherein active inverter states excluding short circuit states acting in different space vector directions are used for current control and current rises (10) of the phase currents are detected during said active inverter states. The current rises (10) detected are transformed in a computing unit (7) into a fixed measuring direction coordinate system and further into symmetrical components and at least one of the symmetrical components computed from said current rises (10), which components rotate at double the electric rotational speed, single electric rotational speed and at zero speed, is evaluated, wherein at least the symmetrical components functioning down to zero speed and rotating at double electric rotational speed are evaluated and the electrical rotor position of the machine (4) is determined therefrom. The invention further comprises a circuit arrangement for the method.

Description

"Method for determining the rotor position of synchronously running electrical machines without mechanical encoders"

The invention relates to a method for the encoderless determination of the rotor position of a synchronously running three-phase machine and a circuit arrangement therefor, as described in claims 1 and 9

Synchronous electrical machines, such as permanent magnet synchronous machines, synchronous reluctance machines, electrically excited synchronous machines, etc. require the high-quality field-oriented control usually the information about the

Rotor position to an angle and magnitude suitable current space pointer in the predeterminable by the field-oriented control direction by means of inverter over

imprint current-impressing methods according to the prior art, wherein the power control subordinate to the field-oriented control calculates a voltage space pointer, which is approximately adjusted using a combination of means by means of inverter voltage space pointers. The representable

For example, in the case of a three-phase inverter, voltage-space pointers are six (six) active space-phasors of equal length (which are proportional to the DC-link voltage of the inverter), each offset by 60 degrees (electrical), and two (two)

Null space pointers that are zero in length. The latter occur when all three

Half-bridges of the three-phase inverter are at the same potential, ie either positive or negative DC link potential. The combination of such

Stress space pointers, which usually repeat after a certain time, is called in the literature PWM (Pulse Width Modulation). Classic PWM methods use three of the aforementioned representable voltage space pointers that are in the vicinity of the voltage space vector desired by the controller. These are the right and left adjacent active space pointers and a zero space pointer. Furthermore, it is known that the strand inductances of said machines vary depending on the rotor position. This was already used for rotor position detection without encoder. For example, the prior art (eg [Schrödl, M.: "Sensorless Control of AC Machines", VDI Progress Reports, Series 21, No. 117, VDI-Verlag 1992], or [Rajashekara, K. et al Control of AC Motor Drives ", I EEE Press, Piscataway, USA, 1996, ISBN 0-7803-1046-2]) announced that the current increases in

 Pulse patterns depend to some extent on the strand inductances, which in turn depend on the rotor position due to geometric axisiness (reluctance, due to different magnetic conductivities as a function of the rotor position) and / or due to saturation effects in the magnetically conductive material in the rotor and stator. A disadvantage of the method for the encoderless determination of the rotor position, especially at low speeds was previously that measurement pulses or measurement sequences are impressed that cause acoustic emissions in the form of whistling or noise and also interfere with the current control.

In principle, inverter current regulations are known in which exclusively active in three different room pointer directions active converter states without

Short circuit conditions are used for approximate adjustment of the voltage space vector specified by the current regulation. The disadvantage here is that these pulse patterns could previously be used only for the purpose of current control and thus for high-quality controls continue to encoder for detecting the rotor position were needed.

The object of the invention is to provide a method for encoderless rotor position determination up to and including standstill and a circuit arrangement for this, which avoids these disadvantages and at the same time has a simple structure. THE TASK IS SOLVED BY THE INVENTION.

In the invention, for the first time, e.g. Theory of symmetrical components used in grid voltage analyzes in a completely new field of application, namely for the analysis and evaluation of converter-induced current increase characteristics with regard to

 Rotor position evaluation from inductance fluctuations, taking into account induced voltages. This results in surprising possibilities and advantages that were previously unknown. The application requires the introduction of a new, previously unknown coordinate system in the complex space pointer plane, which is designated by the new technical term "measuring direction-fixed coordinate system." (Known co-ordinate systems are, for example, the stator-fixed, the rotor-fixed or the rotating field-fixed coordinate system).

The inventive method for the encoderless determination of the rotor position of a synchronously running three-phase machine is characterized in that the detected current increases are transformed in a computer unit in a measuring direction fixed coordinate system and further in symmetrical components and at least one of these current increases calculated symmetrical components, which with double electrical speed , Simple electrical speed and zero speed circulating, is used for rotor position determination, wherein at least the working up to zero speed and rotating at twice the electrical speed symmetrical

Component evaluated and from this the electrical rotor position of the machine is determined.

The advantage here is that by using preferably three active show namely to zero speed sufficiently long measurement times for the determination of

Current increases are generated, this information according to the invention for

high-quality and noiseless determination of the rotor position is used, and thus without expensive and failure-prone mechanical rotary encoder or sensors

Auslangen is found, that is only because of measurements of the currents for the purpose of determining current increases, as it is known from the prior art, for example via measuring resistors, the converter-fed machine is controlled and controlled. Thus, a simple mechanical construction of the machine is possible because no positioning of position sensors or encoders is needed, which would also need to be calibrated accordingly.

The basic idea is to use a special PWM that only uses active voltage space vectors and, in addition to the state of the art, to determine the

Rotor position by evaluating the current increases within the PWM, without additional measurement pulses or measurement sequences are required and the

Current control is not disturbed. The advantage of this is that it causes no additional acoustic interference. A PWM that does not use null space pointers is in [Este. Patent AT 503.602B1 "Method and Circuitry for Approximately Setting a Volumetric Space Pointer"] (/ 1 /), which is a method of approximating the

Voltage space pointer specified, which uses only active space pointers. So no zero space pointer is used as with usual PWM patterns. Going beyond this prior art, it is shown in this invention how to evaluate such a voltage sequence using only active voltage space pointers, in addition to approximating the voltage space vector desired by the current control to detect current increases occurring during the active voltage space hands are metrologically accessible to additionally determine information about the current rotor position.

By combining preferably three active hands, there is the advantage that with small resulting Spannungsaussteuergraden, as they occur especially in the low-speed range, the duration of the active pointer remains so long that current increase evaluations are possible with good accuracy. This is not possible with classical PWM methods at low voltage output levels. Specifically, in the present invention at Aussteuergrad "zero" (no voltage on average over a PWM period) all three active pointers involved (eg, u +, v +, w + or u-, v-, w-) equal length and very good In / l / it is specified how the switch-on times of the pointers u +, v +, w + (or alternatively u-, v-, w-) can be calculated from a desired voltage-space vector, eg calculated from the current regulation. ) of this particular PWM can be determined. The recording of the current increases can be done in different topologies. For example, in one embodiment of the invention, the current increases are detected at least in two phases between the output of the half-bridges and the motor terminal. This arrangement offers the advantage that many industrial converters have such current detection.

In a further embodiment of the invention, the current increases in the base points of at least two half-bridges of the converter are detected. This is advantageous if the evaluating arithmetic unit is connected to the DC link in terms of potential, because it can be used to carry out a potential-based current measurement using inexpensive measuring technology.

Is a particularly inexpensive implementation, such as in applications with high

Numbers, necessary, the current increases in the DC link of the inverter can be detected in a further embodiment of the invention.

A high-quality evaluation is shown in a further embodiment of the invention. Using the theory of symmetrical components, the component rotating at a single electrical speed is also evaluated in addition to the component rotating at twice the electrical speed. The advantage with this

Embodiment is that the rotor position is calculated via two channels, wherein the information channel that evaluates the rotating at a single rotor speed component, a signal that contains improved information with increasing speed. As mentioned, the information channel, which evaluates the component rotating at twice the rotor speed, delivers a quality which is largely constant over the speed.

In one embodiment of the invention is an evaluation in case of incomplete detection of the current increases, preferably exclusive detection of the measuring direction parallel Current increase space pointer components made. This is the case, for example, when the current measurement in the DC link is detected via a single measuring element. In this case, the effect of the unrecognized non-masstrichtungsparallelen Stromstiegsraumzeiger- components by an equivalent function, which simulates the circulating with a simple rotor speed flow and speed-dependent symmetrical component, approximately taken into account. The advantage of this is that a very cost-effective solution with good accuracy of the rotor position detection is possible.

According to a further embodiment of the invention, the variables determined according to the rules of the symmetrical components are fed to a computing unit which derive at least one of the state variables "rotor position", "rotor speed",

"Rotor acceleration" and / or "load torque" calculated. This makes it possible, in addition to an improvement of the rotor position by the state model, to determine the rotor speed and optionally the load torque and / or the angular acceleration of the motor shaft with good dynamics.

Finally, in a further embodiment of the invention, the average inverse differential inductance index is used for monitoring the machine condition with regard to impermissible impedance ratios. This can, for example

Winding short circuits, line interruptions, etc. are detected very quickly and appropriate measures are initiated in good time.

Furthermore, the object of the invention is achieved by a circuit arrangement in which the current detection unit is connected to a current and Stroma nstiegsauswertung, which is connected on the one hand with a transformation unit for the transformation of current increases in the measuring direction fixed coordinate system and on the other hand with a

Current control for the transfer of the evaluated streams is connected, and that the transformation unit is connected to an evaluation unit for the evaluation of symmetrical components, which in turn with a state model for transferring the double rotation angle and optionally also a simple rotation angle is coupled and the state model for forwarding a rotation angle, a rotational speed and optionally a size with a field-oriented control is connected, whereupon the control is connected to pass current reference values with the current control and the current control with a purely active voltage space pointers useful PWM unit, the Processing of the set by the current regulator Sollspannungsraumze 22 is connected, and this is connected to the inverter part for control.

It is advantageous hereby that a simple and cost-effective construction is achieved. Another advantage is that from the current increases symmetric components are calculated, which rotate at twice the electrical speed, simple electrical speed and zero speed, with at least the working up to zero speed and rotating at twice the electrical speed symmetrical

Component evaluated and from the electrical rotor position of the machine (4) is determined, so that no position sensors for determining the rotor position are needed, which costs and especially error-prone components can be saved.

Finally, an embodiment is advantageous, in which the evaluation unit is connected to the transfer of the inverse inductance index to the monitoring unit. As a result, an additional engine monitoring in a simple manner possible.

It should be noted that, of course, for example, the current measurement can be realized in different variants, as indicated in the claims (2) to (4).

THE TASK IS SOLVED BY THE INVENTION.

The circuit arrangement according to the invention is characterized in that there is a synchronously running three-phase machine fed by a converter, wherein the system is designed with a current measurement in one of the said variants and the Current measurements are fed to a computer that performs the evaluations according to the theory of symmetrical components and as a result at least the rotor position, often the rotor speed and possibly a load torque estimate or other state variables for field-oriented control, which on the computer system

is implemented, provides.

The invention will be explained in more detail with reference to an embodiment as shown in the drawing.

It shows:

Fig. 1 is a circuit diagram for the encoderless determination of the rotor position of a synchronously running three-phase machine, in a simplified, schematic representation.

In FIG. 1, a converter equipped with a DC link capacitor 2 with DC link voltage between the connection points 3a and 3b is connected via a preferably three-phase inverter part 1 to a synchronously running electric machine 4. A current detection unit 5 supplies the detected currents to a current and current rise evaluation 6 in a computing unit 7, which on the one hand the

evaluated streams 8 to a power control 9 and on the other hand, the evaluated current increases 10 to a transformation unit 11 passes. The

Transformation unit 11 transforms the current increases 10 in the measuring direction fixed coordinate system and forwards them to an evaluation unit 12, which evaluates according to the theory of symmetrical components at least one of the components which rotate at twice electrical speed, with simple electrical speed and zero speed.

Preferably, at least that component is evaluated which rotates at twice the electrical speed. From this then according to equation GL1 (as described above) the space vector ξΙ Ρ or its real and imaginary part, according to the explained

Regulations, calculated and the double electrical rotation angle 13 calculated. It is also possible that the space vector ξΕΜΚ is also evaluated, so that it results in the simple electrical rotation angle 14. If also an evaluation of the

Zero component, this provides the mean inverse differential inductance ξο 15, which may be used for engine monitoring in an optional monitoring unit 25. The determined angle information is, preferably via a

State model 16, which in addition to an improved electrical rotation angle 17 and the rotational speed 18 and optionally further sizes 19, preferably the load torque and / or the angular acceleration of the motor shaft determined, the field-oriented control 20 is provided. On the basis of its setpoint values (for example speed, torque), this field-oriented control 20 calculates current setpoint values 21 according to the implemented control algorithm and supplies these as setpoint values to the current control 9, which calculates therefrom a setpoint voltage space pointer 22 using the evaluated currents 8. This is implemented in the described PWM unit 23 in a pulse pattern, which uses only active voltage space pointer and controls the Ha lbbrücken the inverter part 1 via control commands 24.

It is essential in the invention that the machine 4 is designed without a rotary encoder or position sensor and the control and regulation takes place only via the current detection. Any existing voltage measurement can optionally be used to improve the accuracy of the evaluation. As a result, a very inexpensive and simple construction for the machine 4 is achieved.

In accordance with the invention, a method is described for determining the rotor position of a synchronously running three-phase machine in FIG. 1, which is supplied by a converter. The detected current increases 10 are in a measuring direction fixed

Coordinate system transformed and evaluated according to the theory of symmetrical components at least one of the calculated from these current increases 10 components. The components run with double electrical speed, simple electrical speed and zero speed. Preferably, the working up to zero speed and rotating at twice the electrical speed component and therefrom by known methods of mathematics, the electrical rotor position is determined

Such a measurement and evaluation can be carried out as follows: If one applies a voltage space vector u + (inverter position 1/0/0 of the inverter 1) to the machine, it reacts with a current increase space vector (Δi / Δt) u + = ξυ. (Measuring direction of the voltage space vector u = 0 ° in the stator-fixed coordinate system α, β). The current increase space pointer (Δi / Δt) is known to be defined as (Δi / Δt) = 2/3 * {(Δiu / Δt) + (Δiv / Δt) * exp (+ j * 120 °) + (Δiw / Δt) * exp (-j * 120 °)} with the respective current increases (Δiu / Δt) in line u, (Δiν / Δΐ) in line v and (Δiw / Δt) in line w.

If a voltage space vector v + (converter setting 0/1/0) is applied to the machine 4, it reacts with a current increase space vector (Δi / Δt) ν + = ξν. (Measuring direction v = 120 °) If a voltage space vector w + (converter 0/0/1) is applied to the machine 4, it reacts with a current increase space vector (Δi / Δt) νν + = ξνν. (Measuring direction w = 240 °)

If the machine 4 were at a standstill and had no axis and no resistance, the space vectors ξυ, ξν, ξw formed in a common stator-fixed manner

Coordinate system α, β a pointer triplet offset by 120 ° each. If one represents the three pointers in a "measuring direction fixed coordinate system" (real axis of the measuring direction fixed coordinate system in the direction of the respective measuring voltage space vector), then the space vector shown ξuu, ξνν, ξww form for the case "machine 4 at a standstill, no Achsigkeit and no resistance "three parallel, equally long hands in the real axis. If the machine 4 were at a standstill and had an axis (smaller inductance of the stator coils, for example, in the d-direction of the rotor (d-axis parallel to the axis

Stator coil axis), larger inductance in the q direction of the rotor), the three would

Space vector ξuu, ξνν, ξww have an additional, with the double rotor position about cosinusförmig varying length. The dependence on the double rotor position can easily be explained, since the high inductance occurs twice per electrical revolution (in the positive and negative q-axis), analogously the low inductivity in the positive and negative d-axis. (The definition of the direction of the d-axis is in itself arbitrary, but fixed with respect to the rotor). Would the machine 4 rotate and have no axis (inductances of

Stator coils irrespective of the rotor position), a rotor magnetisation (in the case of permanent magnet-excited and electrically excited machines) or a rotor-oriented operating current over the stator resistance (in the case of permanent-magnet excited, electrically excited and reluctant machines) generates voltage components in the stator coils which rotate synchronously with the rotor position and correspondingly Current increase shares, which also rotate synchronously with the simple rotor position of the machine 4. In this case, the three space vectors ξuu, ξνν, ξww would have an additional, approximately cosinusoidally varying length with the simple rotor position. If one then rotates an axis machine 4, then both effects are superimposed and the space vectors ξuu, ξνν, ξww contain an offset component ξο that is the same in all three hands, a component rotating with rotor speed ξΕΜΚ and a component rotating at twice the rotor speed ξΙΝΡ.

Based on the well-known calculation rules for symmetrical components [Oswald, B .: "Calculation of three-phase networks - calculation of stationary and non-stationary processes with symmetrical components and space vectors". Vieweg + Teubner, 2009, ISBN 978-3- 8348-0617-8], the following 3 components (hereinafter referred to as "INFORM space vector", "EMK space vector" and "mean inverse differential inductivity index") can be determined as follows:

"INFORM space vector" ξΙΝΡ = 1/3 * [t, uu + ξνν * θχρ (-j * 120 °) + ξww * exp (+ j * 120 °)] (1)

"EMF space vector" ξΕΜΚ = 1/3 * [t, uu + ξνν * θχρ (+ j * 120 °) + ξww * exp (-j * 120 °)] (2)

"Mean Inverse Differential Inductive Index" ξο = l / 3 * [ξuu + ξνν + ξνννν] (3)

The argument of the complex INFORM space vector ξΙΝΡ is twice as big

Rotor position 2γ, usually still to be corrected by a metrologically or by a model to be determined load and speed-dependent correction term

2γ = arg (ξΙΝ F) + ΔylNF (load, speed) (4) The amount of the complex IN FORM space vector ξΙΝ Ρ is largely independent of speed, and therefore the complex IN FORM space vector ξΙ ΝΡ may preferably be small

 Speeds are evaluated.

The argument of the complex emf space vector ξΕΜΚ corresponds to the simple one

 Rotor position γ, if necessary to be corrected by a load-dependent and speed-dependent correction term γ = argftEMK) + AvEMK (load, speed) (5)

The amount of the complex EMF space vector ξΕΜΚ due to the induced voltage decreases with decreasing speed, and therefore, the complex EMF space vector ξΕΜΚ can be evaluated preferably at higher speeds.

The mean differential inductance factor ξο can be used to monitor the

 Operating point or to detect errors or impermissible

 Parameter constellations (impedances), such as for the detection of Windungs Kurzschlüssen, winding interruptions, etc. are used. The measured current rise space pointers have in the measuring direction fixed

 Coordinate system following real and imaginary parts (note: "sqrt (3)" means the root of 3):

Thus, equation GL1 provides:

 The argument arg ^ lNF) can be calculated by arctangent formation atan (ImßlNF} / ReßlNF}) and used in equation (4) to calculate the double rotor angle.

Furthermore, equation GL2 provides:

 The argument arg (ξEMK) can be calculated by arctangent formation atan (Ιιτι {ξΕΜΚ} / Re {ξEMK}) and used in equation (5) for the calculation of the simple rotor angle.

If the current rise measurements are incompletely detected, preferably if only the measurement direction-parallel current increases are detected, those terms in RINFN and IMIlNF that contain non-mesa-parallel current increments can be approximated by modeling RssEMK and Ιιτι {ξΕΜΚ} as the simple one

Angular velocity considered circumferential cosine or sinusoidal functions which are defined via flow- and speed-dependent parameterization. This can be determined for example by a reference measurement. This allows a good detection of the double rotor angle even with current or current increase detection only in the DC link. Advantageously, the invention determines the rotor position of a converter fed synchronously running three-phase machine without expensive and failure-prone mechanical rotary encoder, wherein for the current control exclusively in three different

Room zoom directions acting active converter states are used without short circuit conditions. In this case, current increases of the phase currents are detected during these active converter states and transformed into a measuring direction-fixed coordinate system. Measuring direction fixed means that the current voltage regulation pointer preset by the current regulation is simultaneously used as a measurement space vector and forms the basis for a coordinate system which has its real axis in just this measurement direction.

In one embodiment of the invention is according to the theory of symmetric

Components at least one of the calculated from these electricity increases 10

Components which rotate at twice the electrical speed, simple electrical speed and zero speed, preferably evaluated to zero speed working and rotating at twice the electrical speed component and the electric rotor position is determined from this by known methods of mathematics. This offers the great advantage that well analyzable current increases without additional

Measuring pulses are present, which allow an evaluation in the entire operating range including standstill.

The detection of the current increases 10 can take place in different topologies.

For example, in one embodiment of the invention, the current increases 10 are detected at least in two phases between the output of the half bridges and the motor terminal. This arrangement offers the advantage that many industrial inverters have such current detection. Of course it is also possible that by appropriate adaptation of the

Inverter 1 also a full bridge can be used.

For the sake of order, it should be noted that the invention is not limited to the illustrated embodiments, but may also include further embodiments.

Claims

claims 1. A method for the encoderless determination of the rotor position of a synchronously running three-phase machine (4), which is fed via an inverter (3), wherein active for the current control in different room pointer directions active  Inverter states are used without short circuit conditions and current increases (10) of the phase currents are detected during these active converter states, characterized in that the detected current increases (10) in a  Computing unit (7) are transformed into a coordinate direction fixed coordinate system and further into symmetrical components and at least one of these current increases (10) calculated symmetrical components, which rotate at twice electrical speed, simple electrical speed and zero speed, is used for rotor position determination, wherein at least the up to zero speed working and rotating at twice the electrical speed symmetrical component evaluated and from this the electric rotor position of the machine (4) is determined. 2. The method according to claim 1, characterized in that the current increases  be detected at least in two phases between the output of the half-bridges (u, v, w) and the motor terminal. 3. The method according to claim 1, characterized in that the current increases (10) in the bases of at least two half-bridges (u, v, w) are detected. 4. The method according to claim 1, characterized in that the current increases (10) are detected in the intermediate circuit of the inverter. 5. The method according to at least one of claims 1 to 4, characterized in that in addition to the rotating with double electrical speed component and the peripheral element with a simple electrical speed component is evaluated. 6. The method according to at least one of claims 1 to 5, characterized in that when incomplete detection of the current increase (10), preferably  exclusive detection of the measuring direction parallel current increase space pointer components, the effect of the unrecognized, preferably not masstrichtungsparallelen Stromstiegsraumzeigerkomponenten by a  Replacement function that simulates the circulating with simple rotor speed flow and speed-dependent symmetrical component is approximately taken into account. 7. The method according to at least one of claims 1 to 6, characterized in that the determined according to the rules of the symmetrical components variables of a computing unit are supplied, the at least one of the state variables "rotor position", "rotor speed", "rotor acceleration" and / or Calculated "load torque". 8. The method according to at least one of claims 1 to 7, characterized in that the mean inverse differential inductance index is used to monitor the machine state with regard to impermissible impedance ratios. 9. Circuit arrangement for carrying out the method according to at least one of claims 1 to 8, characterized in that the current detection unit (5) is connected to a current and current increase evaluation (6), on the one hand with a transformation unit (11) for the transformation of current rises ( 10) is connected to the measuring direction fixed coordinate system and on the other hand with a current control (9) for transferring the evaluated streams (8) is connected, and that the transformation unit (11) with an evaluation unit (12) for  Evaluation of symmetrical components is connected, in turn, with a state model (16) for the transfer of the double angle of rotation (13) and optionally in addition to the simple angle of rotation (14) is coupled and the state model (16) for forwarding a rotation angle (17), a rotational speed (18) and optionally a variable (19) is connected to a field-oriented control (20), whereupon the control unit (20) is connected to current regulation (9) while passing current command values (21), and the current regulation (9) is connected to a PWM exclusively used for active voltage space Unit (23) formed for processing the current regulator (9) passing the target voltage space pointer (22) is connected, and this is connected to the inverter part (1) for control. 10. Circuit arrangement according to claim 9, characterized in that the  Evaluation unit (12) for transferring the inverse inductance index (15) to the monitoring unit (25) is connected.